President Hugo Chávez was facing serious allegations over Venezuela's links to Colombian guerrillas last night after Interpol bolstered the credibility of intercepted rebel documents.

The international police organisation announced that a two-month forensic investigation of laptops seized in a raid by Colombian security forces concluded they belonged to the Revolutionary Armed Forces of Colombia (Farc).

Leaks from the trove of 16,000 files and photographs have suggested high-ranking Venezuelan officials plotted to help the Marxist group to obtain weapons and funding for its decades-long insurgency against the Colombian state.

Ronald Noble, Interpol secretary general, said his experts had found "no alteration of the data by Colombian officials". Internationally accepted methods for handling computers were not always followed, he said, but Bogotá had not modified, altered or created files. Interpol said the amount of information - 37,872 word documents and 210,880 photographs - was much greater than previously thought.

Analysts have cautioned that Farc's internal memos may contain misinformation or wishful thinking.

Chávez's ideological affinity with South America's most powerful guerrilla force is no secret and earlier this year he negotiated the release of six hostages held in their camps. Providing logistical support would be a radical escalation given that the US and the EU list Farc as a terrorist organisation which trafficks cocaine.

Venezuela's president has rubbished the documents as fakes and an attempt by the US and "imperialist lackeys" in Bogotá, his conservative rival, to smear his self-styled revolutionary socialism. Chávez was due to rebut Interpol's findings at a media conference last night.

Ecuador's president Rafael Correa, whose leftist government is also accused of conspiring with Farc, said the documents "prove absolutely nothing" and were an attempt by Colombia to justify its cross-border attack on a Farc camp inside Ecuador. The controversial March 1 raid killed at least 25 people, including senior rebel commander Raul Reyes, yielded three laptops, three USB memory sticks and two external hard disks, which have been dubbed Farc's "brain".

In one leaked email dated January 2007, Farc's top military leader, Jorge Briceño, tells the rebels' governing secretariat that he plans to ask Chávez for a loan of $250m (£128m), "to be repaid when we take power". Other leaked documents suggest Venezuelan officials served as middlemen with Australian arms dealers.

Republican hawks in Washington have pushed for Venezuela to be listed as a state sponsor of terror along with Syria, Iran and North Korea. The White House, hostile to Chávez but wary of disrupting Venezuelan oil imports, has soft-pedalled the issue by asking Caracas to explain why some officials were "conspiring against a democratic neighbour".

The controversy will overshadow a summit of European and Latin American leaders which opens today in Peru, with angry exchanges likely between the Andean delegations.